To rank a page the search engine has to find the page.
This may seem very obvious. And it is. Just put in the effort to verify that all of your webpages have links leading to them.
You can not control content on other websites, but you can control content on your own website. So, make sure that at least one page on your site points to any given page.
Each page on your website should offer something new -- something unique.
If you have two or more pages with the same basic content then what is the search engine to do? They are getting smart enough to filter out the page stuffers. So, don't look like a page stuffer.
If you find two pages with nearly identical content, delete one of the pages and change links in your site to refer to just the one page.
Or, if there is an important reason for having the two pages, add some unique content to the twin page.
The title and description (found in the meta-tags area of the page header) count in SEO.
Look to see that the title of a page relates to the page.
Look to see that the description describes the page.
There is much debate about the exact optimal title length. I have seen numbers ranging all over the place -- from "less than 60" to "less than 100". Many developers have recommendations in the 60 to 70 range. At the moment, I target titles less than 64 characters. This number is near the target figure of many SEO practitioners and w3.org recommendations
Apparently it is allowed to have descriptions of pretty much any length. However, if you look at Google SERP (Search Engine Results Page) you will notice that they cut off the description at 160 characters. So that would seem to be to be a nice target length for a description.
H1 should be the main title for your page. This should contain keywords related to your page, and a glance at the H1 phrase should tell an individual more or less what the gist of the page is.
H2 can be used for sub-headings. This will count in SEO and it helps individuals jump to the part of the page that may have most interest for them.
You have have been to websites with urls that contain & ? - session ids and a score of other stuff. These are typically CMS (content management system) sites such as those created in Joomla, WordPress, Drupal, ModX, etc. If you are working with such a system do what you can do to convert these page links to SEO Friendly. This will involve "mod re-write" for websites hosted in Linux and Apache. For Windows hosted websites apparently IIS-redirect will do that trick. Whatever the case is, when you use CMS make sure to turn on SEO friendly urls.
Worst case: "click here". If the text in your link is the only thing used to determine the nature of the content on the target page then the search engine will be mislead into thinking the page is about "click" and that you have "clicks" on that page.
If the page content relates to "Guitar Tab for Stormy Monday" then use that in the link text.
For some purposes having your domain name appear in the href link is best. This will add bulk to your page, and it can make site construction a little more difficult. But it also can help in SEO. As a rule of thumb include the domain name unless there is a reason not to.
If you have reason to suspect that a website might be using spamming techniques or other blant content asking for a "google slap" then don't link to them. You are judged by the company you link to.
This could have been mentioned right at the beginning of this page. Not because it is more important -- it just happens to be easy to do and makes so much sense in so many different ways. We use W3C HTML Validator to validate our pages. You'd be surprised at the "oops" that can be found and fixed this way. Every step of the process helps.
This is more of a philosophical reminder to be clear about what you are doing. If you are clear on the purpose and content of the website you are working on, that will naturally translate into you taking steps that optimize the content.
Speaking of clarity. If your website has redundant pages remove them. For example if your root folder contains a welcome.html, default.html, and index.html page. Either use 301 redirect to point to one page, or delete the redundant pages.
As you may have noticed, sometimes people type in domain.com, other times they may type in www.domain.com. This can dilute your web presence. To avoid this you can use redirect services (depending upon your web host) to convert all domain.com requests into www.domain.com requests.
Jim Thatcher has a good course on image alt tag text use. I recommend you study it. This course is designed to teach you the best approach for using image (img) alt tags for usability. This sometimes may not follow the latest fad in SEO. However, it is good design, and good usability. Eventually this will be to your benefit.
Ultimately it will come down to user experience. The better the user experience, the more value the user gets from your site the better. SEO (search engine optimization) is something you use to make a good better rank better. Start first with a good page, then use SEO to make sure the world can find it.